Combination heater



LSMUMQ' J. A. POWELL COMBINATION HEATER Filed Aug. 18. 1929 Ud. 14 119m,

Patented Urt. ld, i924.

tiri

COMBINATION HEATER.

Application filed August 18, 1920.

T 0 all whom t may concern Be it known that l, JAMES A, POWELL, a citizen of the United States, and a resident of Reading, in the count-y of Ber rs and State of Pennsylvania., have made new and useful Invention in Combination Heaters, of which the following` is a speciication.

This invention relates to. feed water heaters and has for an object the` production ot' a heater which will operate effectively under widely varying conditions ot steam and water tlc-w without occasioning` waste of steam.

A further object is the production et a heater having all the advantages of a jet type and also of a tray type heater and which eliminates the objectionable features oi both these t-ypes of heaters.

A further object is the productionoi an improved feed water heater in which improved means are employed for venting the heater for thepurpose ot discharging1 the air or non-ciondensable vapors, which may be delivered thereto with the steam or water.

These and other objects which will be made more apparent throughout the further description oi the invention are attained by means ot a` heater embodying the features herein described and illustrated. ln the single sheet of drawings accompanying and forming a part hereof, I have diagrammatically illustrated a. heater embodying my invention.

lt is well established that the overall etliciency of a power plant is increased by heating the feed water before it is delivered to the boilers. To accomplish this most economically it is necessary to avoid al waste of heat in the expulsion of air or non-condensab-le vapors from the heater. Two losses are occasioned by improperly venting` heat-ers: First, the heat carried away from the heater with the air or non-condensable vapors occasions a loss; and second, the increased pressure in the heater, occasioned by an excessive amount of air present, causes the auxiliary apparatus, exhausting into the heater, to operate a-t a materially increased back pressure and consequently the economy of the auxiliary apparatus will be much poorer than would be the case it the heater were properly vented. It is usual in power house practice to heat the feed water with steam exhausted from one or more oi the steam driven auxiliaries. It

Serial No. fl4=,44=4.

is well understood that the flow of water to a heater is governed by the load on the main power generating unit, while the flow of steam from the auxiliaries is more constant. `With heaters now in use, it is considered best to so proportion the auxiliaries delivering steam to the heater that the heater will perform. economically at the most constant load on the main generating unit. lVith loads above or below this most constant load, there will be a loss of etliciency due, under an abnormal load, `to improper venting; of air, or, under a subnormal load, to excess steam. rll`he load on the auxiliaries of a power plant is usually substantially constant; consequently, each auxiliary delivers a substantially `constant amount or' exhaust steam per unit ot time. ln proportioning the delivery of steam to the heater, the approximate amount ot steam necessary to accomplish the desired preheating` is ascertained andthe requisite number ot auxiliaries are connected so as to exhaust into the feed water heater. Under such conditions, the amount of exhaust steam delivered to the heater is substantially'constant; whereas, as has been said, the delivery of water to the hea-ter varies with the load on the main units. This occasions temperature iuctuations within the heater, and a. consequent loss when the temperature is above or* below the most economical temperature, which is governed by the i'low of steam and water with constant pressure within the heater. lVith i'eed waterheaters, such as are now in use, the range ot permissible temperature fluctuations is limited, and in addition, the heaters are so constructed that they not only waste steam under conditions of low water flow, but actually accentuate the waste `by `occasioning` an increase in the delivery of heating steam to the heater under conditions ot low water flow. Thisv increase in the amount o-:t heating steam delivered is occasioned by the tact that the decrease in the amount of feed water delivered `to the heater decreases the capacity of the heater to absorb heat and thereby condense the steam delivered to it. The surplus steam in the heater increases the back pressure on the auxiliaries and this in turn makes it necessary ior `the auxiliaries to receive more steam in order to accomplish the work required of them. As. a result, the governing mechanisms of the auxiliaries automatically deliver more steam to the auxiliaries and the auxiliaries exhaust more steam into theheater. 'Ihe surplus steam deliveredv to the heater must be discharged therefrom and it is ordinarily vented tothe atmosphere with a resultant Waste of heat and` also of water. The Waste of heat reduces the efficiency of the entire plant and primarily which operatesiwith high efficiency under Widely. varying conditions of, Water flow..

Referring to the drawings: In the drawings, I havey illustrated in verticali section. a cheater, embodying my invention. 'Ihe casing 3 encloses a heating. chamber4`'and also acollecti'ng chamber 5, which receivespre'heated feed Water combined with the condensate resulting from the condensationofxsteam Within the chamber 4. The

i' casingis also provided at o r nearA its. upper .end With a steam admission port 6, through whichy `steam-is delivered toA the heating l chamber. This. port: may communicate with Y theexlia'ustfportsof. oneor. more auxiliaries or 1t may` communicate .With any suitable sourceofsteam supply. A s shown, Water to ber heated. is` delivered. through. a port 7 toanannular chamber 8, Which surrounds they cylindrical .casingf 3, 'Ifhis chamber is adapted to deliver Water to spray, nozzles 9,

which are arranged in a seriesaround the internal wallofythe` chamber8 and` are con.-

l structedi .to break up the jets ofi Waterv issue ing from` them Ainto a.y mass :ofseparatedrops or sprays and to discharge thespray in such a Wayfthat it is intimately mixed:v with the steam entering. the port 6 and. passing through the chamber 4;y As shown, the

y spray nozzles 9areadapted:to dischargethe Water in substantiallyfhorizontal jets to- `Wardthe centerof the casing 3. With this arrangement, a barrier.A composedz of:v water.

l spray. or `a mass ofjseparate dropsof WaterA isinterposed lbetween. the. portI 6 and the chamber; 4: 4during` normal. conditions of Water flow; consequently, all the steam en.- tering` the heater Will beintimately mixed with .thefsprayand Willnot onlygive up its. heat to the Water in its Apassage -through the heater, but Will be condensed." Under conditions of low waterflow., therozzles 9 are not capable `of delivering a suiiicient, amount of-vvatei"A to formthe necessary. spray barrier. andconsequently, the mixing oflthe, steam ,Y and .'Water is,.no`t.'as effective, nor .is the complete condensation of,` the`l steam accom,- plished. Itis, therefore, necessary to .p ro.

vide means for accomplishing the necessary heat transfer from the steam to the Water under conditions of low flow. In the heater illustrated, I have provided trays 10 in the heating chamber 4 so located and arranged that Water issuing from the nozzles 9 will be received by the trays under all conditions of water flow. With this arrangement, the feed Water Will not only be retained in the heater in contact with the steam, but will be broken up into a mass of drops or thin curtains in overiiowing from one tray to another and finally to the collecting chamber 5. The upper tray 10 may be an annular tray so disposed within the heating chamber thatit will receive the smallest quantity of Water issuing from the spray nozzles 9. It may alsov be provided With notches 11 for the purpose of insuring a substantially uniform delivery ofv Water around its overflow edges, and also for insuring a breaking up of the overflow into a mass of4 separate drops or minute streams. Any number of trays may be employed, and they willy preferably be so arranged that the lower trays receive at least a portion of the Water overiowing the upper trays. With such an arrangement, the feed 'Water' is notv only retained for an appreciable period Within the heating chamber, but it is broken up into sheets, curtains, or minute streams as it falls through the heating chamber toavard the collecting chamber 5. As shown, I have interposed a converging annular apron or baH'le 12 between the heating chamber-and the collecting chamber 5. This apron is so arranged that all Water issuing from the chamber 4 and striking it is ydeflected toward the center ofthe casing 3 and enters the collecting chamber. through a port 13, which is materially less in, area than.- the cross sectional area of the heating chamber, 4.4 The apron surrounds what may be termed a combining. passage, which tendsy to more or less unite the separate streams of Water falling throughr the chamber 4 and. to render the Water more. effective asA an air entraining medium. rIlhe apron 12 also vsliieldsan air offtake port 14, through which aiu and noncondensable vapors accumulating in the heater are discharged, Any suitable means for exhausting the heater may be employed, andif the heater isl designed to operate with an. internal pressure less than atmospheric pressure, it may be; equippedl with an air pump or air ejector Which communicates With the, port 14. It Will, of course, be apparent thatl the port- 14 may communicate directly Withthe atmosphere, if the` conditionsv are such,L that the normal, pressure Within the heater, isA above atmospheric pressure.

In the drawings, I have shoWn.,apump 15 arranged to Withdraw the heated` feed Water fromthefcollecting chamber 5. As shown,

the inlet 1G of the pump communicates directly with the collecting chamber.

The operation of the heater is, in general, as follows: The condensate or water available for feed water purposes is delivered to the port 7 under a head, which will promote sufficient flow through the nozzles 9 to break up the streams issuing from the separate nozzles into a mass of separate drops or sprays. The spray so formed encounters r is encountered by the heating steam entering the heater through the port 6. The intermingling of the steam and water occasions a heat transfer from the steam to the water and a resultant condensation of at least a portion of the steam. Even under normal conditions of water flow, the trays 10 receive water issuing from the nozzles 9, and function to retain the water in the heating chamber and discharge it in the form of curtains, or a multiplicity of streams downwardly through the heating chamber and the combining passage, into the collecting chamber 5. Consequently, any steam which passes the ring of nozzles`9 is subjected to the cooling action of the water retained within the trays 10 and also of the water falling from the trays through the chamber 4. It may be desirable to so proportion the trays that they will accomplish of the heating under normal conditions of flow. This, of course, means that the nozzles will be so arranged and constructed that the jets issuing from them will accomplish 75% of the heating under normal operating conditions. It will be apparent that a decrease in the flow of water through the nozzles will materially incapacitate the nozzles; First, because the heat absorbing capacity of the water will be decreased due to the fact that less water is delivered; and second, because the nozzles will be incapable of adequately breaking up the water into a mass of separate drops or sprays. The water issuing from the nozzles under such conditions wjill be less intimately mixed with the incoming steam and will be less effective in taking up heat from the steam. If the trays 10 were not interposed in the path of incoming water, the water would fall directly through the heating chamber into the collecting chamber, and as a result, a decrease in the flow would occasion a material reduction in the heat absorbing capacity of the water. The trays, however, retain the water, are subjected on all sides to the steam within the heating chamber 4, and are so located and arranged that the water overflowing from them falls in a subdivided condition from one tray to the next as it progresses toward the collecting chamber. This materially minimizes the loss occasioned by. a reduction in water flow and, as a matter of fact, produces a feed water heater which will operate effectively and efficiently throughout a wide range of variations in water liow. It will, of course, be apparent to those skilled in the art that as the spray issuing from the nozzles 9 becomes less effective as a heat absorbing and steam condensing medium, the trays become more elfective. This results from the fact that under normal operating conditions, the temperature within the heating chamber is low, whereas, the temperature in this chamber increases as the water liow decreases. This increasing temperature increases the difference in tempera-ture between the steam and the water and consequently, increases the heat absorbing capacity of the water conytained within and overflowing the trays 10.

In addition, the decreasing flow through the jets increases the length of the period during which the water is retained in the trays.

One of the principal features of my invention is that the air or non-condensable vapors issuing from the heater are withdrawn from the heater at a point of minimum air saturation or point of greatest air pressure. This is advantageous, because it prevents a waste of steam and also because the air and vapors so withdrawn are heavier than would be the case if they were withdrawn from a portion of the heater subjected to the heat of the incoming steam. This last mentioned advantage is important where means, such as an ejector or an air pump is employed for accomplishing the discharge of air from the heater. It is usual practice to locate the air vent port of a heated at or near the top of the heater. Consequently, heating steam is discharged through these ports with the air. This occasions a waste of steam and a resultant reduction in the efficiency of the heater. Most heaters are so designed that this waste is maintained at a minimum under normal conditions of operation. It has, however, been stated that such heaters are ineective under conditions of low water flow and that their ineffectiveness results in an increase in the amount of steam delivered to the heater and a material increase in the pressure within the heater. This pressure will relieve itself through the vent with a re sultant waste of steam. In addition, the accumulation of air within the heater decreases the heat absorbing` capacity of the heater, since the air4 acts somewhat as a heat insulator. Air is also objectionable because it occasions back pressure on the auxiliary supplying steam to the heater, and

this back pressure is independent of the steam condensing capacity of the heater. llVaste of steam is obviated with a heater embodying my invention, since under the worst conditions of flow, steam must pass around the trays and through at least one of the curtains of water dropping from the trays and finally through the cone-shaped mem-l passage 'tends to entrain the air and noncondensable lvapors and to deliver them to the collecting` 'chamber partially compressed y Cv cru

or at least4 vreduced in volume by reason of thecooling .action of the water. As a result, the heating chamber 4 is maintained relatively free ofair und-er widely varying conditions lof water fiow.

Another 4feature ofy my invention is that it embodies the desirable characteristics of both the spray and thef tray type 1 heater. The spray heater is very efficient while operating under normalor moderate conditions of water flow but is exceedingly inefficient 4 under .conditions of low iow. On the other hand thetray type heater is efiicient under conditions of lowv water flow'. Inaddition,

spray Aor jet type of heater is employed.

While VVl have illustrated and described Vwhat I now considery yto be the preferred embodiment of my invention, it will be apparent tothose skilled in the art. that .various changes, substitutions, omissions and additionsmay bemadef-to the apparatus illustrated without departing from the sp-irit and 'scopeiof my invention as set forth bythe appendedA claims.

` What I claim is:

' l. A feed water heater comprising a casing having a steam inlet port and a water inletfport'near the upper end thereof, 'a water discharge' port near the bottomthereof and an -air `discharge portbetween .the

steam inlet -portand the water 4discharge port, in combination with nozzles loc-ated withiin the casing and Communicating with the water` inlet port for delivering water in the` form of spray'. across :thepa'th of the steam entering the'steam inlet port, and trays located below said nozzles and adapted -to receive'water delivered therefrom.

'2.-A feed water heatercomprising a casinghaving a steam inlet port and a Water inlet port located near the top thereof and a water discharge port and an air oiftakc port located near the bottom thereof, in comination with means communicating with the water inlet port for delivering a mass of spray across the interior of the chamber, trays llocated within Athe casing below said means and adapted to receive water therefrom, and a combining cone located between said trays and the air offtake and water discharge ports. y

y 3. A feed water heater comprising a casing having a steam inlet port, and a water inlet port located near the top of the casing,

an air offtakeportand a water discharge 'f port formed therein, means located within the casingand communicating with said water inlet port for discharging a Water spray across the interior of the casing, means located within said casing below vsaid first mentioned means for collecting water discharged therefrom and for delivering a multiplicity of streams of water through the interiorof the casing, and-a downwardly converging cone-shaped member between said means and said air olftake port.

4. A feed water heater comprising a casing having a steam inlet port adjacent the upper end, a water discharge port adjacent the lower end, and an air offtake port intermediate said inlet and discharge ports, a series o-f spray nozzles located within the casing and communicating with said water inlet port for discharging a water spray across the interior of the casing, a series of trays located within .thecasing between the nozzles and the air offtake port and adapted .to receive water from said nozzles, and u;

converging combining cone located between said trays and said water discharge port and forming a shield for said air olfta-ke port.

5. In a feed water heater, a casing having a steam port formed in the top thereof, a water inlet port, located adjacent saidsteam port, a water discharge port located nean the bottom thereof, and an air offtake port between .the water inlet port andthe water discharge port, in combination with a series of nozzles commimicatino with the water inlet port andlocated Within the casing adjacent .,saidwater inlet portfor discharging a spray of water across the interior of the casing, a series of trays located. within .the casingbelow said nozzles anda downwardly converging combining cone, located below said trays and above said air o'take'port y In testimony whereof, I have hereunto subscribed my name'this 4th day of August,

- JAMES A. POWELL.

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